British Pat. Specification No. 481,909, published in 1938, teaches the para directing effect of BF.sub.3 -phenolate catalysis on the alkylation of phenols with C.sub.5 -C.sub.12 mono-olefinic hydrocarbons and polymers thereof, specifically C.sub.12 -C.sub.18 mono-olefinic polymers, at reaction temperatures in the range of 0.degree. to 100.degree. C. U.S. Pat. No. 2,655,544, issued Oct. 13, 1953, extends said teaching to the alkylation of phenol with C.sub.18 -C.sub.24 mono-olefinic hydrocarbons. U.S. Pat. No. 3,360,464, issued Dec. 26, 1969, further extends such BF.sub.3 -phenolate catalysis teaching to the alkylation of phenol with 500 to 3000 molecular weight (i.e., about C.sub.36 to about C.sub.214) mono-olefinic hydrocarbons such as a polymer of ethylene, propylene, butylene, isobutylene, or amylene.
British Pat. Specification No. 1,159,368, published July 23, 1969, confirms that the BF.sub.3 -phenolate catalysis of the alkylation of phenol with a mono-olefinic polymer of propylene or isobutylene of polymer carbon content from 50 to 20,000 (molecular weight range of about 700 to about 280,000) results in an alkylphenol product whose alkyl-substituent is (by infrared spectrum analysis) more than 95% p-alkyl-substituted.
In the foregoing patents, whenever removal of BF.sub.3 portion of the BF.sub.3 -phenolate catalyst is mentioned, the disclosed removal of BF.sub.3 from the alkylation reaction mixture is by water and/or caustic washing or by treatment with ammonia or amine to form a filterable ammonium-BF.sub.3 solid complex. British Pat. Sepcification No. 481,909 mentions BF.sub.3 recovery and reuse without teaching any specific method therefor.
However U.S. Pat. No. 3,000,964, issued Sept. 19, l961, teaches BF.sub.3 recovery from and recycle to the alkylation of phenol with C.sub.3 to C.sub.20 mono-olefinic hydrocarbons in the presence of BF.sub.3 -phenolate catalyst through the use of an inert hydrocarbon boiling in the range of 30.degree. to 200.degree. C, preferably a C.sub.5 to C.sub.9 alkane, which, when added to the alkylation reaction mixture, lowers the boiling point of the resulting mixture so it boils at a temperature within the range of 50.degree. to 175.degree. C, preferably from 100.degree. to 175.degree. C, at atmospheric pressure. Such boiling mixture of hydrocarbon entrainer and alkylation reaction mixture is refluxed under distillation conditions whereby BF.sub.3 -phenolate dissociates, and BF.sub.3 gas is carried by hydrocarbon entrainer vapor to a partial-condenser wherein the hydrocarbon entrainer is condensed but remains as a BF.sub.3 gas. The hydrocarbon entrainer condensate is returned to the boiling mixture. The BF.sub.3 gas is absorbed in liquid phenol at a temperature of 40.degree.-100.degree. C to reform BF.sub.3 -phenolate catalyst for recycle to the alkylation reaction. The quantity of the hydrocarbon entrainer used to so remove BF.sub.3 amounts to 30 to 200 weight percent of the alkylation reaction mixture.
While the BF.sub.3 removal technique of the 1961 Patent was useful for the preparation of C.sub.3 to C.sub.20 (43 to 281 M.W.) alkyl-substituted phenol, it would not be a suitable technique for BF.sub.3 removal from the fluid reaction mixture obtained from the alkylation of phenol with a 500-3000 M.W. polymer of propylene or butylene because boiling and refluxing of the mixture of entrainer hydrocarbon and such alkylation reaction mixture would occur at temperatures which would cause substantial molecular weight degration of the desired high molecular weight alkylphenol product by fragmentation of the polymeric alkyl-substituent and attendant alkylation of unreacted phenol with the fragments.
Such fragmentation of the phenol's alkyl-substituent derived from the 500-3000 M.W. propylene or butylene polymer also occurs to the polymeric hydrocarbon alkylating agent during the alkylation reaction, as pointed out in British Pat. specification No. 1,159,368. Said patent indicates that both fragmentations are inherent to acidic catalysis required for the alkylation of phenol but teaches that the fragmentations can be minimized by use of BF.sub.3 -phenolate as the acidic catalyst in amounts of from 0.1 to 0.5 mole per mole of the polymeric alkylating agent and conducting the alkylation reaction within the temperature range of 0.degree. to 60.degree. C. By the use of such alkylation reaction conditions and by use of 1.0 to 3.0 moles of phenol per mole of the 500-3000 M.W. propylene or butylene polymeric hydrocarbon alkylating agent, the resulting fluid reaction mixture contains about 65-85% of 475-1800 M.W. alkyl-substituted phenol product, 2-12% C.sub.3 -C.sub.12 alkylphenol by-product mixture, 3-22% phenol, and 2.5 to 6.0% BF.sub.3 -phenolate. The difference in molecular weight between the 475-2800 M.W. alkyl-substituent and the 500-3000 M.W. polymeric alkylating agent and the formation of the by-product alkylphenol mixture result from BF.sub.3 -phenolate fragmentation. The alkane component of the fluid alkylation reaction mixture is a molecular species inherent to the polymeric propylene or butylene as will be later described.
The C.sub.3 to C.sub.20 mono-olefinic hydrocarbon alkylating agents used to prepare alkylphenols according to the 1961 Patent mentioned before and its resulting C.sub.3 -C.sub.20 alkyl-substituent do not, as far as the teachings of said patent are concerned, undergo fragmentation in the presence of BF.sub.3 -phenolate catalyst during either the 40.degree. to 120.degree. C alkylation reaction or the boiling of the mixture comprising the hydrocarbon entrainer and the fluid alkylation reaction mixture at the preferred temperature range of 100.degree.-175.degree. C used to remove BF.sub.3 from attendant dissociation of BF.sub.3 -phenolate catalyst.
However, the fluid alkylation reaction mixture from the phenol alkylation with 500-3000 M.W. propylene or butylene polymer alone or combined with 30 to 200 weight percent of C.sub.5 to C.sub.9 alkane hydrocarbon when heated above 70.degree. C either during reaction or after the completion thereof is accompanied by rather substantial fragmentation of the polymeric alkylating polymer or the desired 474-2800 alkyl-substituent on the alkylphenol product. For example, heating the alkylation reaction mixture containing an 1823 M.W. alkyl-substituted (substituent from butylene polymer) and to a temperature of 70.degree.-71.degree. C before removing the BF.sub.3 -phenolate catalyst, causes a 72% decrease in molecular weight of the alkylphenol product.
British Pat. No. 1,159,368 establishes that the use of a SAE 5-40 mineral oil reaction diluent for the alkylation of phenol with the 500-3000 M.W. propylene or butylene polymers will further supress fragmentation of the polymeric alkylating hydrocarbon during the alkylation reaction in the presence of 0.1-0.5 mole of BF.sub.3 -phenolate catalyst even permitting use of alkylation reaction temperatures in the upper portion of the 0.degree.-60.degree. C reaction temperature range, i.e., 45.degree.-60.degree. C, to produce alkylphenol products of molecular weight equal to or higher than the molecular weight of alkylphenol products produced at reaction temperatures in the range of 20.degree.-25.degree. C. The use of mineral oil reaction diluent and 45.degree.-60.degree. C reaction temperature provides optimum product molecular weight in commercially feasible reaction time. Such use of mineral oil reaction diluent also substantially reduces the viscosity of the resulting alkylation reaction mixture. For example, for alkylphenol products of substantially the same molecular weight the products produced had Universal Saybolt Second (SSU) viscosities at 99.degree. C of 17257, 1943 and 985 SSU when the alkylating butylene polymer reactant weight concentrations were 100%, 68% (32% SAE-5W oil), and 60% (40% SAE-5W oil) respectively. Thus the use of mineral oil diluent provided the two advangages of permitting higher reaction temperatures without contributing greater fragmentation of the polymeric alkylating hydrocarbon thus producing lower molecular weight alkylphenol product and providing a much lower viscosity product.
The use of mineral oil reaction diluent is advantageously employed by combining the mineral oil with the propylene or butylene polymer reactant. Such reactants have SSU viscosities at 38.degree. C in the range of 400 to 788,000. By the use of from 30 to 70 weight percent of the crankcase, e.g. SAE-5W to SAE-40 mineral oils based on the polymer in the present inventive process, the transfer of polymer to the alkylation reaction, conduct of the alkylation reaction, processing of said reaction mixture from BF.sub.3 removal through recovery and transfer of the high molecular weight alkylphenol product and further use of such product are not flow limited by high fluid viscosity. The SAE-5W and SAE-10W oils have the respective centistoke viscosities at -18.degree. C of below 860 and below 2600. The SAE-20, 30 and 40 oils have centistoke viscosities at 100.degree. C respectively of between 5 and 10; 10 and 13; and 13 and 17.
British Pat. No. 1,159,368 further discloses that the high molecular weight alkylphenol products from the alkylation of phenol with 500-3000 molecular weight propylene or butylene polymers are useful as intermediates for the preparation of a variety of lubricant oil addition agents which, in general, are produced in the presence of mineral oil as reaction medium. Thus the use of mineral oil to reduce viscosity of the polymeric alkylating hydrocarbon and as alkylation reaction diluent is of further advantage in that such diluent need not be removed from the high molecular weight alkylphenol product before its ultimate use in preparing lubricant oil addition agents.
British Pat. No. 1,159,368 teaches the use of a C.sub.5 -C.sub.8 alkanes as solvent for phenol in the preparation of BF.sub.3 -phenolate catalyst, for the polymer of propylene or butylene, and as reaction diluent. In the illustrations of such uses of alkane diluent the alkane (n-hexane) retained in the reaction mixture after completing the alkylation reaction amounts to from 25 to 60 weight percent based on the other components of the reaction mixture. However, the alkane was not used in any BF.sub.3 removal method. Rather BF.sub.3 was removed either by water extraction or by reaction with ammonia to form a filterable solid complex.
The 500-3000 M.W. propylene or butylene poymeric alkylating hydrocarbons used to prepare the 475-2800 M.W. alkyl-substituted phenols are commercially available products obtained from propylene or butylene polymerization in the presence of Friedel-Crafts type catalyst. The commercial polymerizations, in general, use AlCl.sub.3 or BF.sub.3 as catalyst. Such polymerizations produce a product which contains about 5-15 percent saturated alkane molecules and 95-85 percent substantially mono-unsaturated molecules of the same number average (M.sub.n) molecular weight. The alkane molecules result from hydrogen redistribution during polymerization and have in their hydrocarbon chains the same units as contained in the saturated portion of the mono-unsaturated molecules. The propylene polymers contain repeating saturated isopropylene units with the unsaturated molecular specifies being terminated by a single isopropenyl unit. The butylene polymers are more complex. While the butylene polymers can be prepared by the polymerization of isobutylene, they are, in general commercially prepared by the copolymerization of refinery butene streams which contain both isobutylene and normal butenes or such refinery streams enriched with isobutylene. The isobutylene polymers contain repeating saturated isobutylene (2,2-dimethyl ethylene) units with the unsaturated polymer molecules terminated by a single unsaturated unit. The copolymers of isobutylene and normal butenes have in their saturated chain or saturated chain portion mainly saturated isobutylene units with some normal butylene units concentrated at one end with the unsaturated molecules of the copolymer terminated at the other end by the single unsaturated unit. In the unsaturated molecular species of both the isobutylene polymers and the copolymers of isobutylene and n-butenes, the terminal unsaturated units are trisubstituted or vinylidene units present as the ##STR1## radicals, wherein X is mainly ethyl but also methyl resulting from terminal structure isomerization taking place after the polymerization reaction and before quenching of the catalytic activity.
The alkylation of phenol occurs only by the addition of the foregoing mono-unsaturated molecules to a ring carbon. The addition is mainly (over 95%) to the ring carbon in para position with respect to the ring carbon having the hydroxy-substituent. By such addition to the para-carbon, its hydrogen saturates the single double bond of the foregoing radicals. Thus the product of such addition reaction is an alkylsubstituted phenol, not an alkenylphenol whose substituent retains the double bond.
The foregoing reaction of 1.1-3 moles of phenol catalyzed by 0.1-0.5 mole of BF.sub.3 -phenolate per mole of 500-3000 M.sub.n propylene or butylene polymer diluted with 30 to 70 weight percent of mineral oil produces a viscous fluid alkylation reaction mixture which contains the 475-2800 M.sub.n p-alkyl-substituted phenol product, 500-3000 M.sub.n alkane, C.sub.3 -C.sub.12 alkylsubstituted phenol by-product, unreacted phenol, mineral oil and BF.sub.3 -phenolate catalyst. Boiling of the mixture of such viscous fluid alkylation reaction mixture and from 30 up to 200 weight percent thereof of an inert C.sub.5 to C.sub.9 alkane in a distillation column as a means for removing BF.sub.3 according to the technique of the 1961 would have no practical value because such boiling, even if possible, would cause drastic molecular weight degradation of the desired 475-2800 M.sub.n alkyl-substituted phenol product.
However, it has been discovered that an alkane hydrocarbon having a normal (760 mm Hg) boiling point within the range of 80.degree. to 125.degree. C (hereafter 80.degree.-125.degree. C boiling alkane) can be effectively used to remove BF.sub.3 from the viscous fluid alkylation reaction mixture containing the desired 475-2800 M.sub.n alkyl-substituted phenol product. Such inventive use of the 80.degree.-125.degree. C boiling alkane does not involve boiling the mixture of such alkane and said viscous liquid alkylation reaction mixture. Rather the inventive use of the 80.degree..gtoreq.125.degree. C boiling alkane is that of a stripping aid for the removal of dissociated BF.sub.3 gas from the viscous fluid alkylation reaction mixture because the relatively high molecular weights of components of the viscous liquid alkylation reaction mixture would not likely boil and reflux at temperatures necessary for dissociation BF.sub.3. The present inventive use of the 80.degree.-125.degree. C boiling alkane involves dissolving it in the viscous fluid alkylation reaction mixture and heating incremental portions of the solution to simultaneously dissociate BF.sub.3 -phenolate and vaporize the dissolved alkane.
Merely adding the alkane to the viscous fluid alkylation reaction mixture will not cause the alkane to become dissolved in a useful short time for continuous operation. Rather such "adding" will, because of the differences in both specific gravities and viscosities, cause the formation of two liquid layers; a top alkane layer and a bottom viscous fluid layer. Vigorous mixing of the liquid alkane and the viscous fluid is required to dissolve the alkane.
Hence, the present inventive BF.sub.3 removal is based on an inventive concept differing in kind from the BF.sub.3 removal concept of U.S. Pat. No. 3,000,964. Moreover, successful application of the present inventive concept to BF.sub.3 removal from the viscous fluid alkylation reaction mixture depends upon technical effects not present in the use of C.sub.5 -C.sub.9 alkanes according to said 1961 Patent.